Where is the File Format Version Stored?

[Werni2A]

Over time the file format changed little by little. e.g. geometric shapes like rectangles or ellipses introduced an attribute for hatch style at some point. During parsing it's important to know with which file version we interact as there is e.g. a hatch attribute stored or not.

I searched for it a while but don't even have an idea which value (offset) could be considered. The amount of files does not make it much simpler, probably the version is not saved in the actual symbol file itself as I have searched it pretty thoroughly but rather in a centralized file.